For two weeks in December, climate change was on everybody's mind. Representatives of 193 countries gathered in Copenhagen for the most concentrated effort to date to forge a strong international strategy to reduce global warming.

U.S. President Barack Obama underlined the urgency of the moment when he said that "climate change poses a grave and growing danger to our people. All of you would not be here unless you, like me, were convinced that this danger is real. This is not fiction. It is science."

But two months later, the effort to fight global warming seems mired in uncertainties.

The Copenhagen conference failed to reach any formal agreement binding countries to lower their levels of man-made greenhouse emissions. Instead, it set a goal of limiting global warming to 2 degrees centigrade above preindustrial levels by 2050, but left it to individual countries to set their own pace of progress.

And, while the summit's final accord called for rich countries to transfer hundreds of millions of dollars to poor ones over the coming years to help them cope with climate change, it left open the question of who will donate how much, where the money will go, and who will oversee the spending.

But these limited results are only some of the reasons why it is becoming difficult to predict where the drive to reign in greenhouse emissions worldwide goes from here.

'Climategate'

Another unexpected legacy of Copenhagen is the controversy that arose in the run-up to the conference over whether leading climate scientists have been objective in arguing that man-made emissions are the main factor behind warmer global temperatures.

U.S. President Barack Obama said in Copenhagen that climate change "is not fiction. It is science."

That controversy, dubbed "Climategate," centers upon e-mails written by climate-change investigators at one of the world's main centers for climactic research, Britain's University of East Anglia. Just ahead of Copenhagen, hackers posted the e-mails on the Internet as alleged evidence of the investigators' intolerance of opposing opinions.

Critics of the UN-led effort pointed to the e-mails as proof for their long-standing charge that the public is being led into a costly attempt to manage nature by scientists who barely understand the mechanisms of climate change themselves.

Some of the most vocal criticism took place on the sidelines of the Copenhagen conference. That included suggestions that one of the most quoted phrases from the e-mails, "hide the decline," could be evidence that the East Anglia climate scientists tried to hide data that contradicted their theories. The phrase appeared in an e-mail written in 1999 by the head of the East Anglia Climactic Research Unit, Phil Jones.

One member of a U.S. Senate delegation at the summit, Senator James Inhofe (Republican, Oklahoma), said the words "hide the decline" meant the author was urging other researchers to "hide the decline in temperatures." The charge was rejected by the climate researchers at East Anglia, who said Jones' e-mail was referring only to the need to find a better way to chart the overall rise in temperatures at the time despite contradictory results coming from one measurement tool: the analysis of tree rings.

Over this example and many others, both sides accused each other of selectively publicizing only parts of the e-mails and waging a "sound-bite" war to sway the public against or in favor of the Copenhagen process.

David Whitehouse, an adviser to the London-based Global Warming Policy Foundation, says the e-mail controversy has had a major impact on the climate debate.

"The interesting thing that has changed over the past few months is that the debate, the scientific debate about what is going on, is now a lot healthier, a lot more open," Whitehouse says, "and you get people who only a few months ago, or a year ago, were saying that the science is settled, the debate is closed, are now saying, 'Well, there are considerable uncertainties.'"'Clear And Present Danger'

Whitehouse predicts the debate Climategate generated will have a direct influence on the next UN-led climate-change summit, scheduled to be held in Cancun, Mexico, in November.

"We have a global financial crisis, and some governments will be looking for reasons not to sign up to treaties that will cost them a lot of money or hamper their development," Whitehouse says. "So, some governments will look at the science and say, 'Yes, the science is more uncertain, we need to think about this because what we thought was certain a few years ago is now less so.."

Former UN climate chief Yvo de Boer was frustrated at the lack of agreement in Copenhagen.

If so, that would be a major blow to the United Nations' hopes for Cancun to make further progress toward the kind of binding accord among countries that Copenhagen fell short of.

At the start of Climategate and since, UN leaders have said their faith in the scientific basis for tackling emissions remains unshaken.

"Nothing that has come out in the public as a result of the recent e-mail hackings has cast doubt on the basic scientific message on climate change," UN Secretary-General Ban Ki-moon said in New York in early December. "And that message is quite clear -- that climate change is happening much, much faster than we realize, and we human beings are the primary cause."

On February 24, Ban urged delegates from world weather agencies meeting in Antalya, Turkey, to "reject last-ditch attempts by climate skeptics to derail your negotiations." Ban said in a statement read at the meeting, "Tell the world that you unanimously agree that climate change is a clear and present danger."

The consensus that man-made activities are the major cause of global warming is held by all the national science academies of all the major industrialized countries. It was first expressed by the United Nations in 2007, when the Intergovernmental Panel on Climate Change found that human actions are "very likely" the cause of global warming, meaning a 90 percent or greater probability.

But efforts to build momentum for Cancun in November could be hampered by still another aftershock of the Copenhagen conference, the resignation of the UN's chief climate negotiator, Yvo De Boer.

De Boer, who is widely reported to be disappointed with the inability of world leaders to forge a formal accord in the Danish capital, said on February 18 that he will leave his post on July 1, ahead of the scheduled end of his term in September.

As he made his surprise announcement, he said talks toward a global agreement were "on track," but that he was uncertain a full treaty could be finalized this year.